A reference herein to a patent document or other matter which is given as prior art is not to be taken as an admission that that document or matter was, in Australia, known or that the information that it contains was part of the common general knowledge as at the priority date of any of the claims of the present application.
Electrostatic loudspeakers use a thin flat diaphragm usually consisting of a plastic sheet, for example such as Mylar™, impregnated or covered with a conductive material capable of holding an electric charge, for example such as graphite, located between two electrically conductive grids supported by frames, known as stators, with a small air gap between the diaphragm and stators. The diaphragm, by means of its conductive coating and an external high voltage which is applied to it, is held at a DC potential of several kilovolts with respect to the stators. The stators are driven by the audio signal, the front and rear stators being driven in counterphase. As a result, an evenly distributed electrostatic field proportional to the audio signal is produced between both stators. This causes a force to be exerted on the charged diaphragm and its resulting movement drives the air on either side of it, providing an acoustic output.
The stators should generate as uniform an electric field as possible, while still allowing for sound to pass through, that is, they need to be substantially acoustically transparent, and generally need to be very flat. They can therefore be difficult to manufacture because of the required degree of accuracy.
An object of the present invention is to provide methods for manufacturing a stator for an electrostatic loudspeaker which allow accurate, relatively low cost production.